1. Field of the Invention
The present invention relates to a robot control APPARATUS and method for controlling a robot arm that is driven to follow a specified trajectory, based on an instruction value to be instructed against a drive source corresponding to each of multiple joints.
2. Description of the Related Art
In recent years, industrial robots that perform assembly and the like in a factory have been demanded to adapt to production speed improvement and complex movement, and have been demanded to increase their movement speed. In order to increase the movement speed of a robot, steep acceleration and deceleration is required in joint drive. On the other hand, the robot includes a speed reducer, a belt, a bearing, and the like as transmitting components for transmitting a drive force from a drive source (actuator) to a joint, but particularly the speed reducer generally has low rigidity, and hence vibration easily occurs when steep acceleration and deceleration is performed. When this vibration acts on the transmitting components, those transmitting components are overloaded, which is not preferred from the viewpoint of durability.
In view of this, there has been proposed an apparatus configured to estimate the load to be applied to the transmitting component during the robot movement by a disturbance observer, detect the overload through comparison with a threshold value, and perform processing of protecting the robot when the overload is detected (see Japanese Patent No. 4335286).
Further, there has been proposed an apparatus configured to calculate the magnitude of the vibration in the robot based on vibration characteristics, optimize the trajectory by incorporating the magnitude of the vibration in an evaluation function, and control the robot with use of the optimized trajectory (see Japanese Patent Application Laid-Open No. 2011-167827). With this, it is possible to reduce the vibration to be generated during the robot movement.
The technology described in Japanese Patent No. 4335286 can protect the robot, but when the overload is detected during the robot movement, it is necessary to proceed to the processing of protecting the robot, which leads to a problem that the takt time is affected.
Further, the technology described in Japanese Patent Application Laid-Open No. 2011-167827 can reduce the vibration to be generated during the robot movement, but even if the vibration is reduced, the load torque that acts on the transmitting component is not always reduced. In other words, for example, as the rigidity of the transmitting component becomes higher, the vibration is reduced, and hence the movement speed may increase by the calculating method described in Japanese Patent Application Laid-Open No. 2011-167827, but when the transmitting component is brittle, the transmitting component may not be able to withstand the increased movement speed. That is, even when the trajectory to reduce the vibration is calculated, the load torque to be applied to the transmitting component is not always reduced, and hence there is a problem in that the durability of the robot is not always improved through the reduction of the vibration.